1. Field of the Invention
The present invention relates to a method of carbon monoxide conversion and a method of hydrogen-containing gas production. More precisely, it relates to a CO conversion catalyst comprising copper, alumina and a metal oxide such as zinc oxide or the like, with which carbon monoxide in hydrogen-containing gas is converted into carbon dioxide and hydrogen in the presence of steam and oxygen, and to a method of carbon monoxide conversion and a method of hydrogen-containing gas production in which is used the catalyst.
2. Description of the Related Art
Known are various techniques of producing hydrogen through hydrocarbon reforming. In particular, many techniques of hydrocarbon reforming with steam have been industrialized. In these, used are nickel-based catalysts, with which methane, LPG, naphtha and others are processed to give hydrogen for petroleum refining. Techniques of partially oxidizing heavy hydrocarbons such as vacuum residues with oxygen to give hydrogen have also been industrialized. Recently, many studies have been made in using hydrogen as produced according to the hydrogen production methods noted above as the fuel for fuel cells, and are now being in industrialization stages.
In the hydrogen production methods, in general, carbon monoxide gas (CO gas) as produced in the first steam reforming reaction is converted into hydrogen and carbon dioxide in the next shift reaction. In particular, for fuel cells in which CO gas is a catalyst poison, CO gas must be fully removed from hydrogen. For that purpose, in general, CO-containing gas is oxidized with steam through high-temperature shift reaction and low-temperature shift reaction to thereby lower its CO content. JP-A 56-158147, JP-A 5-245376 and JP-A 64-27645 disclose copper-aluminium-zinc-based catalysts, copper-aluminium-magnesium-based catalysts and copper-aluminium-chromium-based catalysts for low-temperature shift reaction. However, the CO conversion is limited in the shift reaction with steam.
Known is an example of CO gas removal through low-temperature CO conversion with an oxidizing agent of oxygen (Soviet Union Patent, SU217383A790618). The CO gas removal method disclosed comprises high-temperature shift reaction followed by CO gas conversion with steam and oxygen, which is for increasing the degree of CO gas conversion and for increasing the yield of hydrogen. In the method, used is a zinc-chromium-copper-based catalyst in the CO conversion step that follows the high-temperature shift reaction step. They say that the catalyst is applicable to a gaseous system having a CO content of at most 1%. One preferred embodiment disclosed comprises removing carbon dioxide prior to the CO conversion step. Therefore, the method in the SU patent is defective in that the hydrogen-containing gas production step therein is complicated, and that the CO conversion therein is limited like in the shift reaction with steam (in Examples of the SU patent, the CO conversion is about 90%).
The invention has been made in consideration of the matters noted above, and its object is to provide a method of converting CO in a hydrogen-rich gas as generated in steam reforming of hydrocarbons or the like, with steam and oxygen into hydrogen and carbon dioxide to a high degree of CO conversion, to provide a method of hydrogen-containing gas production through CO conversion, and to provide a catalyst for CO conversion.